Apparatus used in the analysis of chemical and/or biological properties of a sample and in sample preparation take on a variety of shapes and forms. Despite their variety, most of these apparatus include common mechanisms that are designed to selectively hold an object, such as a slide, test tube, etc., as the object is transported or otherwise manipulated in the system.
One such apparatus is set forth in U.S. Pat. No. 5,804,145, to Gao et al. The '145 patent is directed to an apparatus for making blood smears on microscope slides. During the blood smearing process, a microscope slide is received and carried by a slide truck. The truck comprises a body portion having a slide-receiving platform as its bottom surface. The platform has a recess formed therein that communicates with a vacuum port. When a vacuum is applied to the port while the platform is closely spaced from a microscope slide, the slide is drawn to and held against the platform by the pressure of the vacuum. The truck, carrying the slide, moves along a predetermined path as blood is smeared across the surface of the slide.
Another apparatus adapted to analyze blood is set forth in U.S. Pat. No. 5,209,903, to Kanamori et al. The '903 patent includes a conveyor for handling and transporting sample blood through a blood analyzer and an automatic blood smear generator that is placed under the control of a programmable controller. In accordance with one aspect of the apparatus, a printer is used to print unique identifiers on each slide. To this end, a printer head of the printer is positioned directly above a slide as the slide is supported on a guide plate. The guide plate steps the slides under the printer one at a time as the identification codes are printed on them. A holder is used to hold the slide during this printing process. The holder comprises a pair of arms that are pivotally attached to a common support. The arms are disposed to rotate toward and away from one another and are driven by a piston that is connected to a pneumatic source. Protrusions that extend from each arm close over opposite edges of the slide to hold the slide securely against the guide plate while the identifying code is printed.
An apparatus for use in an automated chemical analyzer is set forth in U.S. Pat. No. 5,882,596, to Breeser et al. The '596 patent discloses a vessel shuttle that can be used for moving reaction vessels, such as test tubes, to or from an assay resource station in the analyzer. The shuttle has a plurality of movable plates that are adapted to move cooperatively with respect to one another to advance a vessel stepwise along a linear path without a corresponding net motion of the carrying plates during the advancement. Each plate supports a plurality of the vessels in corresponding fixed slots formed in the plate.
The foregoing apparatus use pneumatic drives and/or complex mechanical arrangements to achieve the desired grasping, transport and/or manipulation of the test objects. In apparatus employing pneumatic drives, a separate pneumatic/vacuum system is provided thereby increasing the overall cost and complexity of the apparatus. Similarly, complex mechanical arrangements increase manufacturing costs as well as cost of ownership due to reduced reliability. Accordingly, an apparatus for selectively holding and releasing an object in an analysis system that is less mechanically complex and has simplified drive requirements is desirable in many situations.